When e.g. an old or badly maintained floor is to be brought in order, it is typically planed/ground off, before it is finished with oil or varnish.
The apparatuses used are typically floor planes/floor grinding machines with either a number of round plates with circular grinding wheels or a grinding cylinder with enclosing grinding belt. Do-it-yourself people experience that it is difficult to achieve uniform grinding of the floor, and that a large amount of grinding wheels or grinding belts are to be used.
The problem with these apparatuses is that dust and/or ground material burns into the grinding wheel/grinding belt, either due to the floor being greasy or due to residues of varnish or lacquer on the floor. This means that it is often necessary to replace the grinding wheel/grinding belt, causing increased costs.
In order to prevent burn-in of dust and/or ground off material, it has been found that simultaneously with grinding cooking oil or similar may be used, but this measure complicates the grinding process.
If floor planes/floor grinding machines are used with rotating round plates with circular grinding wheels, a uniform grinding of the floor is not achieved by running the floor plane/floor grinding machine across it, entailing that time and effort is to be used in moving the floor plane/floor grinding machine back and forth several times.
Another problem with apparatuses where only grinding wheels or grinding belts are used is that these are very exposed if there are nails, screws or other protruding parts on the floor, which thereby may tear apart the grinding wheel or the grinding belt. This entails that the grinding wheel or the grinding belt is to be replaced, even if it is not worn down, and furthermore possibly entailing damage to the round plate or the grinding cylinder, as these are disposed in immediate vicinity of the floor.
In order to achieve sufficient grinding, it is necessary that the round plate or the grinding cylinder are applied a constant pressure down against the floor, entailing that these apparatuses are typically very heavy apparatuses which via their self-weight provides for applying weight upon the round plate or the grinding cylinder. However, the problem is that the apparatus becomes very heavy and cumbersome to transport, and the grinding may easily occur too deeply into the floor if care is not taken.
In U.S. Pat. No. 6,425,813 is disclosed an apparatus for grinding floors and which is provided with a rotating round plate, where circular grinding wheels are used, and where it is the self-weight of the apparatus that provides for the pressure on the circulating round plate.
In U.S. Pat. No. 5,224,301 is disclosed an apparatus for grinding floors and which is provided with a rotating grinding cylinder, where a grinding belt is used which encloses the grinding cylinder, and a tightening wheel. Both apparatuses have one or more of the previously mentioned drawbacks.
In DE A1 42 26 681 is disclosed an apparatus for surface cleaning, and which is provided with two counter-rotating cylinders which may be provided with a number of grinding elements. Furthermore, exhaust of dust and abraded material occurs through a pipe connection. The apparatus is mounted with height adjustable wheels for holding the cylinders at a certain distance from the underlying surface.
In EP A1 0 261 685 is disclosed an apparatus for grinding floors, and which has two grinding cylinders rotating about their own longitudinal axis and about a common point. The apparatus is mounted with height adjustable wheels for holding the cylinders at a certain distance from the underlying surface.
DE A1 42 26 681 and EP A1 0 261 685 have the same disadvantages. For example, they are both large and heavy apparatuses which cannot be easily be lifted by one person, and the weight entails that they may be difficult to manoeuvre. Furthermore, both apparatuses have been fitted with spacers in the form of height adjustable wheels, which is not an advantage as the grinding drums cannot optimally follow the contour of the underlying surface, but the spacing between grinding drum and underlying surface will instead be determined by the contour of the underlying surface at the spots where the wheels are running.
Furthermore, mobile apparatuses for grinding surfaces are known from U.S. Pat. No. 1,904,893, U.S. Pat. No. 1,271,639 and GB 1 038 395.
The apparatuses known herefrom include horizontally oriented grinding cylinders which are enclosed by screens. None of these documents disclose division into an outer and an inner screen which are movably connected, or designs that enable either the inner or the outer screen being divided into a plurality of separate screen members which are mutually movably connected.